Automotive engines include a system for recirculating exhaust gases from the engine exhaust system to the engine combustion chambers. The recirculated exhaust gases mix with the air and fuel delivered to the combustion chambers and inhibit the formation of nitrogen oxides during the combustion process.
A conventional exhaust gas recirculation (EGR) system includes a vacuum operated EGR valve assembly that controls the flow of exhaust gases to the combustion chambers. In some EGR systems, a solenoid operated valve unit is used to regulate the vacuum and thereby allow electronic control over the flow of recirculated exhaust gases.
This invention provides a solenoid operated vacuum regulator valve unit that assures repeatable operation when used to regulate the vacuum in a vacuum operated EGR valve assembly.
In this vacuum regulator valve unit, a cylindrical valve member is mounted loosely on a shaft and slides into and out of engagement with a valve seat that surrounds an air inlet port. When the valve member is engaged with the valve seat, it interrupts air flow through the port to allow an increase in the vacuum (a decrease in the pressure) that operates the EGR valve assembly. When the valve member is disengaged from the valve seat, air flows through the port to decrease the vacuum (increase the pressure) that operates the EGR valve assembly.
The valve seat is formed by a thin washer supported on a valve body, and the air inlet port opens through the washer to an air inlet passage in the valve body. To assure repeatable operation of the vacuum regulator valve unit, we have found that the washer must fully engage the valve body at the perimeter of the air inlet port. This invention provides a vacuum regulator valve unit having a valve body constructed to camber the washer and thereby assure that the washer does fully engage the valve body at the perimeter of the air inlet port.
Moreover, we have found that to assure repeatable operation of the vacuum regulator valve unit, the valve member must fully engage the valve seat. This invention provides a vacuum regulator valve unit having a shaft constructed with an undercut taper to articulate the valve member and thereby assure that the valve member does fully engage the valve seat.
The details as well as other features and advantages of the preferred embodiments of this invention are set forth in the remainder of the specification and are shown in the drawings.